Distros: that's exactly why I've ended up with Debian, over and over again. I'll install something else, spend a weekend getting it working, learn all sorts of interesting stuff, and then get frustrated at all the little things I have to do to make it a satisfactory experience. I then go back to Debian, where everything just works. (I tried Ubuntu once; it was just different enough from Debian to really irritate me, but not enough that I was really learning anything.)

>>>For example, if I am writing an essay/code and I have to switch to command line to type in a long command to access some book somewhere in my system then in the heat of the moment command line would just drive me crazy. <<< See, for me it's the opposite: the command line is perfectly natural, almost more like an extension of myself, but GUIs drive me nuts. I think that's just a personality thing.

Other resources online: you seem to have already discovered MIT's OCW. I know other universities (e.g. Yale) have similar programs, but they're nowhere near as extensive as MIT's, and they tend not to have what I want. I've also found course websites from all sorts of universities useful.

If you can get access to a good research library, that's enormously helpful, as a lot of things (e.g. TAoCP) just aren't online.

And of course Wikipedia is awesome; I often use its "references" and such for textbook recommendations.